[usecase-webapi] improve ResourceTime w3c usecase

- Show image after loading it
- Group the timing checkpoint in a div
- Use table to format the information
- Add a margin to this div

Impacted tests(designed|approved): new 0, update 1, delete 0
Unit test platform: [Tizen IVI][Android]
Unit test result summary: pass 1, fail 0, block 0